Waterbased finish choice?

[melandy]

I'm closing in on the point where I need to make some decisions on how to do the finish on the 000 I'm building. Before anyone asks, I'm pretty set on the idea of using a sprayed on waterbase finish.

 

I used Color Tone sanding sealer and finish from StewMac on the uke I built a couple of years ago, and I had planned on using the same on this build, but they no longer carry it. They still have other Color Tone products, just not the sanding sealer and finish.

 

They have a new line of products (new since I built the uke at least) from Target Coatings, but the reviews on the website are unflattering. The finish itself has 3.5 out of 5, but the companion products (sealer, pore filler, etc) are all 1 out of 5. I did read the reviews and not just look at the numbers, and the anecdotal evidence on the finish puts it in a better light.

 

Another option would be KTM-9 from LMI. There is not a review system in place on LMI's site, so the only customer comments there are what LMI put there, which perhaps obviously, are all positive. KTM does not have a separate sanding sealer. You would use the same stuff for sealing and finish, which in theory would make things simpler.

 

So, anyone have experience with Target Coatings and KTM-9? Would you recommend one over the other (or something else entirely)?

 

LMI recommends their new system 3 pore filler. I'm not remotely crazy about that idea. It's a multi-part epoxy filler that you still have to color. Sounds like way too much hassle to me. They also say that another epoxy based filler (ZPoxy) is compatible.

 

Given that they specifically say that epoxy based filler is compatible, would a waterbase precolored porefiller (such as color tone from stewmac) work with KTM when they recommend something very different, or would that be like crossing the streams?

[Freeman Keller]

You probably knew I would chime in, eh Andy? I have used three different finishing systems in my short building career - here are my experiences

 

1) StewMac rattle cans of lacquer. Imho nitro is still the best, but it is dangerous, toxic, explosive, stinky... It gives thin coats that flows well, each coat melts in to the last, buffs out beautifully. I sprayed two in my garage, the third in a true paint booth - I risked blowing up the neighborhood, killed the spotted owls in the back yard, stunk up my wife's car and damaged a few brain cells.

 

2) So, I next used the old SM Colortone water base (over their paste filler). Sprayed with a small syphon jam gun and home compressor. The finish is OK compared with nitro but does not have the depth of gloss and maybe has a slight blueish tint. I did get some witness lines until I learned the strick of misting with alcohol before each coat (I'll return to this).

 

3) After seeing some of Mike Doolin's beautiful guitars and reading his endorsement of KTM-9 at LMI I tried it on my next few. First over SM paste pore filler (bonds fine, do a wash coat first), then over Zpoxy. I did a little test on some koa of SM paste, CA and Zpoxy as pore fillers - in that order they get better at popping the grain and harder to apply/level. I did a masking tape pull test and got no separation on any of the pore fillers.

 

I am spraying the KTM-9 with a little gravity "HPLV" gun and a small 8 gallon compressor, water filter and pressure regulator (about 40 psi if I recall). I've used a coat of shellac on spruce to seal it, but on koa, mahogany, rosewood and maple I've just shot two wash coats diluted about 50:50 with denatured alcohol. One of the real tricks with any waterbased is when you clean your gun (with warm soapy water), put a little DA in the cup and shoot it out the nozzle, then leave some in the cup. Next day scruff sand to 320 or 400, then shoot a light mist of the DA, dump the gun and pour your KTM into it (I keep the extra lacquer in a small jar so I don't have to keep opening the can). Shoot the KTM immediately - depending on temp and techique you may want to dilute slightly with DA. The mist coat makes the surface slightly tacky - coats don't melt like nitro but they do seem to adhere better. I have had no witness lines since I have been doing this.

 

If you let the KTM cure for 30 days before buffing it seems to give a better gloss than the SM Colortone, but still not as good as nitro. I also don't believe my finish is as thin as nitro, but I've never measured it. I'm happy with KTM-9 and will continue to use it, but there are others who feel very differently

 

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=34535

 

I'll also add that I have no experience with the Target product - it does get discussed in the finishing sections of MIMF, OLF and the kit forum. Another option is French polish, which I have also never used.

 

The following threads have pictures of some of my guitars finished in KTM-9

 

http://acapella.harmony-central.com/showthread.php?2638065-Build-thread-koa-tricone

 

http://acapella.harmony-central.com/showthread.php?2816860-Koa-twins

[melandy]

 

You probably knew I would chime in, eh Andy? I have used three different finishing systems in my short building career - here are my experiences

 

 

With as much as you've helped me I hate to pester you directly, but yes, I'm very glad you chimed in!

 

Thanks,

-A

[Freeman Keller]

Good resources

 

http://www.mimf.com/cgi-bin/WebX?14@227.MPhvawDbJt3.0@.ee6b6a8

 

(also if you are a MIMF member, look at their archives)

 

http://www.luthiersforum.com/forum/viewforum.php?f=10101&sid=208502640792a639fbc61feceb2e4dbc

 

(OLF doesn't have a dedicated finish forum, you'll have to just look at thread titles)

 

http://www.kitguitarsforum.com/board/viewforum.php?f=6&sid=5eca96cf34a4486292912f33ab3cfbe1

 

http://www.kitguitarsforum.com/archives/forum.php?which=finishforum

 

(the last one is an old forum that has died, but the first topic seems to be about a Target finish. Don't know if its the SM stuff)

 

Happy reading

 

btw - I know people also apply KTM with a brush and I did a few small parts that way. If you don't have a compressor/gun that might be an option. I have an article from American Lutherie talking about brushing KTM - I could send that if you are interested.

[MahaloVision]

Finishes are really personal things. You have to try a few out and see what works for you. I can give you a rundown on what I've used water-based wise and you can take it for what it's worth.

 

I have not used KTM-9 yet. All kinds of good feedback on it, but just haven't gotten around to trying it. I did use the previous water-based finish that LMI sold, applied with a sponge brush and rubbed out by hand. Worked OK, but like a lot of water-based finishes it looks a tad blue. Applying with a sponge brush was fairly easy and enjoyable, and sometimes I think about doing it again when I'm setting up the rig for spraying.

 

I've used Target Coatings PSL, USL, EM6000, and EM9000. Had the same problems with PSL that everybody else did, which is that humans destroy it on contact. Had to refinish several guitar necks because the stuff just got eaten away, very soft and dirty looking. It's too bad because it was very easy to apply and rub out. USL was a bit better, and I've got a few out there that seem to be holding up.

 

The EM9000 was used once on an electric solidbody, and I did like it enough that I plan on using it again on another one. Very tough, easy enough to apply and to color with opaque or tint including water-based paints for plastic RC cars. Mixed 50/50 with 9000 and the paint, and the same mix works with the USL. It will look a bit flat but looks very good under gloss topcoats. I did not have a buffer at the time, so rubbed it out by hand, and got decent results. Did see some witness lines but they disappeared after final polishing. A buffer would have been better, and I'm looking forward to it now that I've got it setup. Wouldn't recommend EM9000 on an acoustic, except for possibly the neck and headstock.

 

Just used EM6000 on the Mudroom prototypes. Shoots easily enough, easy to sand, buffs out really well. Not sure what the long term durability is, but seems to be at least as good as the USL was at this early stage. I'd recommend at least a week between final coats and sanding/buffing, possibly longer if you can wait.

 

All of the Target Coatings stuff is going to look just a bit blue, the EM6000 possibly less than the others. I highly recommend adding a few drops of Vintage Amber (TransTint Dyes from Target or Stewmac), straining before putting it in the gun. Takes some of the blue off, adds some warmth, and looks reasonably close to nitro. Just don't go overboard with it. I did not use the Vintage Amber tint on the Mudroom prototypes because I wanted to see how the 6000 would look, and I wish now that I had mixed it in.

 

On the mudrooms, I tried using Crystalac pore filler, and have mixed feelings about it. Easy enough to apply, but requires a few attempts before getting it right. Even with a credit card squeegee, it still came out of some of the pores when sanding back. A couple repeats and it filled with no problem. Color of the filler is not so great although it's supposed to be clear. Might try some with the tint and see how that does.

 

Filling with System 3 epoxy works with the older Target Coatings, and probably would with the EM6000. Probably with KTM-9 too, but again I haven't personally done that. I personally don't enjoy pore filling with epoxy, so I don't do it anymore, but the results were OK by me. You could probably use any kind of hardware store or hobby store epoxy, slow set and/or thinned slightly with alcohol. As always, test on scrap first. Again, it's a personal thing, so see what works for you.

[melandy]

Thanks for the feedback guys. I think I'll give KTM-9 a shot.

 

For spray equipment, I have the smaller of the two siphon guns from stew mac...

http://www.stewmac.com/shop/Finishing_supplies/Equipment:_Spray_equipment/Spray_Guns.html

 

Would that work with KTM-9? Freeman, I ask because you mentioned that you used a gravity feed gun.

 

Capacity on the smaller gun was not an issue with the uke, but it was a lot smaller than a guitar. From memory, it seemed like at the time I could get a day of shooting (4 or 5 coats) out of a cup of finish on the uke, so I should not have an issue with running out in the middle of a shooting session as long as I check the level in the cup before I start.

 

Any idea on how much finish is used (in fluid ounces) in a shooting session?

[Freeman Keller]

 

Thanks for the feedback guys. I think I'll give KTM-9 a shot. For spray equipment, I have the smaller of the two siphon guns from stew mac... http://www.stewmac.com/shop/Finishing_supplies/Equipment:_Spray_equipment/Spray_Guns.html Would that work with KTM-9? Freeman, I ask because you mentioned that you used a gravity feed gun. Capacity on the smaller gun was not an issue with the uke, but it was a lot smaller than a guitar. From memory, it seemed like at the time I could get a day of shooting (4 or 5 coats) out of a cup of finish on the uke, so I should not have an issue with running out in the middle of a shooting session as long as I check the level in the cup before I start. Any idea on how much finish is used (in fluid ounces) in a shooting session?

 

 

I have a gun very much like that and used it with both the old SM waterbased and the first KTM-9 job. It worked just fine, but was acting up a little so I bought a gavity feed gun like this one only because a motorcycle painting friend recommended it

 

http://www.grizzly.com/products/Mini-HVLP-Spray-Gun-Stainless-Steel-Cup/H7670

 

The little gun you have is known as a "jamb" gun in the automotive industry and I think holds 8 oz. I would usually put about half that in it and that would be enough for at least three coats (I do a three per day schedule). I made the mistake one time of buying the small can of KTM from LMI (I think that was 8 oz) - that is not nearly enough to finish one instrument, but the next size can is too much (I pour what is left into a baby food jar to seal it better).

 

I know people do leave finish in the gun between sessions - with the gun like yours I would take the cup off, put a latex glove over the top to seal it, wash the gun with hot soapy water, then stick the siphon tube in a little jar of alcohol and shoot a tiny bit. Water is soluble in alcohol so you are washing any left over water out of the gun to prevent the tip rusting. Every two or three days I take the tip and needle out anc clean everything real well. Next time you cut off a low E string keep the piece - the core is a nice size to clean the tip.

 

I have a piece of cardboard behind where I spray (my "booth") - each time I start by shooting a little bit onto the cardboard so I can check the spray pattern. If there is anything funky I stop immediately, dump the gun and reclean it - everytime the gun wasn't just right I would get runs. I get runs anyway but by the next day they can be sanded out. All of the acoustics I shot hanging, but because I was doing a burst on the LP I put it on a stool in the middle of the shop and shot it flat. I think I got much better coverage (altho I did get some runs on the sides) - big problem of course is that you can only do one side.

 

Again, I think that is one of the real advantages of any lacquer - you can have flaws - runs, dust, bugs - just sand them out and shoot some more. Back in my old street rod days we used to say that 90 percent of a lacquer finish ended up on the floor, what stayed on the car was perfect.

 

A couple more random thoughts after reading Mahalo's excellent reply - I do like Zpoxy but it is hard to apply and level. What I ended up with is one coat full strength (or diluted very slightly with DA), scrape and sand back to bare wood. A second coat diluted maybe 2:1 with DA, sand that back. Then a couple of wash coats of KTM at 1:1 with DA. Then the build coats - 3 a day until you are happy (or run out of finish). Wait at least 2 weeks, sand from 600 to 2000, micromesh if you want to or buff with medium and fine.

[melandy]

 

Then the build coats - 3 a day until you are happy (or run out of finish). Wait at least 2 weeks, sand from 600 to 2000, micromesh if you want to or buff with medium and fine.

 

 

Are the build coats undiluted KTM?

 

I'm going to do my best to force myself to wait a month after the build coats before mucking about with it further.

[Freeman Keller]

I'm not going to quote all of that, but I will try to answer individual questions. First, what a clever holding thingie. I just hang them from a pipe over the top of my cardboard booth and yes, trip over the hose and all the other things that they mention. Basically I hang the body and neck with the back facing out, spray the back and run around the sides, set the gun down and turn the body and neck around, spray the front and then run around the sides again. You have to spary up to get the butt, down to get the neck area - it isn't ideal.

 

When I did the LP the neck was on and masked. I put a wood block in one of the pick up holes that stuck out maybe and inch. I put it flat on a little step stool with the top up, shot a coat running it to the sides, then carefully picked it up and flipped it over onto the neck and the block. I could then shoot the back.

 

 

The whole finish process is more or less documented here - start on page 8 or so. I talk a bit about how I did the burst - there is color both directly into the wood (stain) and in the finish (paint). The LP got two applications of SM amber desolved in DA, the first standed back almost to white. In the actual finish I put two drops of amber into 4 oz of KTM, shot two coats, then added a drop of brown and started the burst from about 6 inches. I then added another drop or two and moved out closer to the edge, then a couple more and about an inch in. Then lots of clear coats.

 

 

http://acapella.harmony-central.com/showthread.php?2843023-Home-made-Les-Paul/page8

 

I also did a traditional tobacco burst on the F5, here was an old thread on that process

 

http://www.kitguitarsforum.com/archives/threads.php?id=765_0_7_0_C

 

Yea, build coats are as thick as you can put on considering temperature and your skill. With nitro or some of the other finishes you can get a matt version with lots of solids, that builds a lot faster and sands easily. I don't think KTM has that. Btw - if you don't have it, Dan Erlewine's book on finishing (StewMac again) is worth it, particularly if you want to do a burst.

[melandy]

Yep. Have the finishing book... They included that in the kit. That's where I picked the colors from. Just gathering as much intel as I can before jumping off this particular bridge.

 

I ordered some finishing supplies today... Colors and filler from stew Mac and KTM from LMI.

 

Still have a lot of work left to do before I start spraying tho.